This invention relates generally to aerospace vehicles, such as airplanes, spacecraft and other vehicles that are designed for use at high altitudes and in outer space and propelled by reaction type motors, and, more particularly, to thrust vector control systems for controlling and steering these types of vehicles.
Aerospace vehicles propelled by a reaction type motor, such as a rocket motor, are generally controlled and steered by some type of movement of the thrust axis of the rocket motor with respect to the longitudinal axis of the vehicle. This type of control of a rocket-propelled vehicle is commonly referred to as thrust vector control. Conventional thrust vector control systems utilize several different approaches for moving the thrust axis of the rocket motor. One conventional thrust vector control system utilizes an articulated exhaust nozzle to deflect the exhaust gas and thereby tilt the thrust axis of the rocket motor with respect to the vehicle axis. Another conventional thrust vector control system employs heat-resistant vanes that are positioned within the discharge portion of the exhaust nozzle to deflect the exhaust gas and tilt the thrust axis of the rocket motor.
Still another conventional thrust vector control system utilizes a rocket motor that is pivotally mounted on the vehicle so that the entire rocket motor can be tilted relative to the vehicle axis. This type of control system usually takes the form of a large, fixed rocket motor that is used only for propulsion and several small, gimballed rocket motors arranged around the outer periphery of the vehicle that are used for steering and control.
Finally, another conventional thrust vector control system relies on lateral displacement of the thrust axis of the rocket motor with respect to the vehicle axis. Several examples of this type of thrust vector control system include a control system that laterally displaces the exhaust nozzle of the rocket motor, as disclosed in U.S. Pat. No. 3,200,587 to Tolson and U.S. Pat. Nos. 3,392,918 and 3,258,915 to Goldberg, a control system that laterally displaces the throat of the rocket motor, as disclosed in the Goldberg references, and a control system that employs a cone-shaped member positioned in the exhaust passage of the rocket motor, as disclosed in U.S. Pat. No. 3,188,024 to Schneider. The cone-shaped member described in the Schneider reference is mounted eccentrically in the inner portion of a ring, the ring being movable within the exhaust passage of the rocket motor to vary the space between the sides of the exhaust passage and the cone-shaped member to force more of the exhaust gas to flow on one side of the cone-shaped member or the other.
Although each of the various types of thrust vector control systems has its advantages, each of the systems also has several disadvantages. For example, thrust vector control systems that rely on some form of interference with the path of the exhaust gas as it exits the combustion chamber have an adverse effect on the efficiency of the rocket motor. This is because a change in the direction of the exhaust path from a straight to an angled path causes turbulence. Control systems that utilize an articulated nozzle require a gastight seal between the movable nozzle and the casing of the motor. Considerable difficulty has arisen when attempting to design gastight seals that will contain the flaming, erosive, high pressure gases ejected from the combustion chamber and still allow the nozzle to be easily moved by lightweight actuators over a practical deflection angle.
Finally, for control systems that rely on a tilting of the thrust axis, the swivel point of the thrust axis must be located well aft of the center of gravity of the vehicle if sufficiently large control moments are to be generated. Likewise, for control systems that rely on a lateral displacement of the thrust axis, the rocket motor must be allowed to move over relatively large lateral distances to generate the required control moments. Accordingly, there still exists a need for an improved thrust vector control system. The present invention clearly fulfills this need.